I. Field of the Invention
The present invention relates to analog circuits. More particularly, the present invention relates to a novel and improved analog switch comprising a balanced mixer.
II. Description of the Related Art
As emerging digital communication systems replace receding analog communication systems, a need arises for the user to be able to communicate using both analog and digital systems. The ability to communicate using both types of systems assures the user that service will be available to him if he is in an area having only an analog system or an area having only a digital system.
To have the ability to communicate using both types of systems, the equipment that the user has must support both types of communication systems. Providing dual mode service can be bulky, expensive, and power inefficient if separate circuits are used for each type of communication system. A more practical design uses as much circuitry as possible for operation in both types of communication systems.
By merging the digital mode circuits and the analog mode circuits at some intermediate point in the signal path, both the digital mode signal and analog; mode signal can pass through the same circuitry thus eliminating the need for redundant circuitry. For example, once merged the digital mode signal path and the analog mode signal path may share power control circuitry, RF upconversion circuitry, or power amplification circuitry.
Therefore the object of the present invention is to provide an inexpensive method of providing a coupling mechanism for dual mode equipment.
A further objective is to provide a switching mechanism using a balanced mixer.